Polyisobutene and polyisobutene derivatives for use in lubricant compositions

ABSTRACT

The invention describes polyisobutenyl derivatives of succinic acid obtainable by: i) reacting a polyisobutene which has a reactive end group content of at least 80% and whose molecular weight distribution is characterized by a maximum M p  in the distribution curve in the range from 500 to 20 000 daltons and a ratio of weight average molecular weight to number average molecular weight M W /M N  of below 1.4 with maleic acid or maleic anhydride; ii) reacting the polyisobutene-succinic acid derivative obtained in i) with at least one compound I which has at least one primary or secondary amino group and/or an OH group to form an amide or ester bond, and also a process for preparing them and their use as additives in lubricant compositions.

The present invention relates to the use of polyisobutenes in lubricantcompositions and also to novel functionalized derivatives ofpolyisobutenes whose polyisobutene radicals are characterized by amolecular weight distribution having a polydispersity M_(W)/M_(N) ofless than 1.4, to a process for preparing them and to the use of thepolyisobutene derivatives as lubricant additives.

Derivatives of polyisobutene which are obtainable by successive reactionof highly reative polyisobutene (PIB) with maleic anhydride (MA) andsubsequent reaction of the reaction product obtained with alcohols,amines or aminoalcohols, also referred to in the following aspolyisobutenyl derivatives of succinic acid or PIBSAs for short, areused in lubricant compositions as dispersants for solid particles suchas soot (see, for example, DE-A 27 02 604 and EP 602 863). Thesedispersants customarily have polyisobutenyl radicals having an averagemolecular weight in the range from 500 to 20 000 daltons.

It will be appreciated that the polyisobutene used in preparing thepolyisobutene derivatives has to have a sufficient reactivity for thereaction with MA. In the reaction of PIB with MA, the olefinic endgroups of the formulae (A) and (B) in particular are accessible forreaction with MA, and the groups of the formula A have the highestreactivity.

For this reason, polyisobutenes having an olefinic end group (groups ofthe formulae A and B) content of at least 80%, and in particular havinga high proportion of end groups A, are desirable.

The prior art teaches the preparation of olefin-terminatedpolyisobutenes by cationic polymerization of isobutene or isobutenichydrocarbon streams in the presence of boron trifluoride complexcatalysts (see, for example, DE-A 27 02 604, EP-A 145 235, EP-A 481 297,EP 671 419, EP-A 628 575, EP-A 807 641 and WO 99/31151). Thepolyisobutenes obtained in this manner have a high olefinicallyunsaturated end group content, in particular end groups of the generalformula (A).

However, the polyisobutene derivatives prepared by functionalizing theabovementioned polyisobutenes do not have satisfactory dispersion andviscosity behavior. In particular, products having good dispersancyfrequently have poor viscometric properties. The dispersancy may beimproved by increasing the molecular weight of the polyisobutene radicalor compensated for by increased additive quantities. However, thisresults in a viscosity increase which is undesirable in particular atlow temperatures, for example with regard to the use of dispersants infuel economy oils.

It is an object of the present invention to provide dispersants based onpolyisobutenes for lubricant compositions which simultaneously have highdispersancy and improved viscosity behavior.

In-house investigations have shown that the moderate viscosity behaviorof conventional polyisobutene derivatives and their moderate dispersancycan be attributed to comparatively high molecular nonuniformity of thepolyisobutene radicals. In other words, the broad molecular weightdistribution of the polyisobutene radicals of these derivatives meansthat polyisobutenes having good dispersancy, i.e. a relatively highaverage molecular weight, contain a high proportion of high molecularweight products which has a disadvantageous effect on the viscositybehavior, while the polyisobutene derivatives having advantageousviscosity behavior, i.e. a low average molecular weight, contain a highproportion of short-chain products having unsatisfactory dispersancy(dispersion stability), so that to achieve sufficient dispersancy,relatively large additive quantities are required, which has theabove-described disadvantages.

The processes disclosed by the prior art cited at the outset deliverpolyisobutenes having a high proportion of reactive end groups. However,the products obtained still have comparatively high proportions of highmolecular weight products. The molar mass distribution of thesepolyisobutenes is accordingly characterized by polydispersity values(=ratio of weight average molecular weight to number average molecularweight) M_(W)/M_(N) of above 1.6.

Polyisobutene derivatives having a relatively narrow molecular weightdistribution of the polyisobutene radicals may in principle be preparedby “living” cationic polymerization of isobutene, see, for example,Kennedy and Ivan “Carbocationic Macromolecular Engineering”, HanserPublishers 1992, and also U.S. Pat. No. 5,169,914. A living cationicpolymerization is the polymerization of olefins in the presence of aninitiator system which comprises a compound suitable for formingcarbocations, for example a benzyl halide or a tert-alkyl halide or acorresponding benzyl or alkyl ether or ester, as the initiator and aLewis acid as the coinitiator. The polyisobutene derivatives obtained inthis manner generally have a halogen atom as the end group and areaccordingly unsuitable for preparing polyisobutene derivatives.

Further in-house investigations have shown that polyisobutenes having ahigh olefinic end group content of more than 80 mol % and a lowpolydispersity may be prepared by “living” cationic polymerization whenisobutene is polymerized in the presence of an initiator system whichcomprises at least one Lewis-acidic metal chloride or semimetal chlorideand at least one compound II having at least one functional group FGwhich forms a carbocation or a cationic complex under polymerizationconditions and is selected from halogen, acyloxy and alkoxy which arebonded to a secondary or tertiary aliphatic carbon atom, to an allylicor to a benzylic carbon atom, in a solvent which is inert toward theLewis acid at a molar ratio of Lewis acid to compound II in the rangefrom 1:1 to 1:100. This process also forms part of the subject-matter ofthe previous German patent applications P 10061727.1 and P 10061751.8.

The high olefinic end group content of the polyisobutenes prepared inthis manner and their relatively high molecular uniformity,characterized by a distribution curve having a polydispersityM_(W)/M_(N) below 1.4, makes it possible to prepare the derivatives ofpolyisobutene according to the invention.

The present invention accordingly relates to polyisobutenyl derivativesof succinic acid which are obtainable by:

-   -   i) reacting a polyisobutene which has a reactive end group        content of at least 80% and whose molecular weight distribution        is characterized by a maximum M_(p) in the distribution curve in        the range from 500 to 20 000 daltons and a ratio of weight        average molecular weight to number average molecular weight        M_(W)/M_(N) of below 1.4 with maleic acid or maleic anhydride;    -   ii) reacting the polyisobutene-succinic acid derivative obtained        in i) with at least one compound I which has at least one        primary or secondary amino group and/or an OH group to form an        amide, imide or ester bond.

The invention further relates to a process for preparingpolyisobutene-succinic acid derivatives which comprises the preparationof a polyisobutene having a polydispersity M_(W)/M_(N)<1.4 as describedabove followed by steps i) and ii).

Polyisobutenyl radicals are those organic hydrocarbon radicals which arecomposed predominantly, preferably of 80 mol % and in particular of 90mol %, of repeating units of the formula [—CH₂—C(CH₃)₂]—.

Preference is given to those polyisobutenes having a polydispersityM_(W)/M_(N) of up to 1.3 and particular up to 1.2. With regard to use asdispersants, preference is given to those polyisobutene derivativeswhose molecular weight distribution has a maximum M_(p) in the rangefrom 1 000 to 15 000 and in particular in the range from 1 500 to 5 000.The number average molecular weight M_(N) is in comparable ranges,.

In principle, useful compounds I include all alcohols, amines andaminoalcohols which have at least one primary or secondary amino group.With regard to the dispersing activity of the polyisobutene-succinicacid derivatives according to the invention, preferred compounds Iinclude alcohols, amines and aminoalcohols which have exclusivelysaturated aliphatic or saturated cycloaliphatic structural units.Preference is given to aminoalcohols and amines which have at least oneprimary amino group. In addition to the at least one functional grouprequired for the reaction of the PIB reaction product with MA, thecompounds I preferably have at least one further, polar, nonionicfunctional group, for example a further amino group or OH group and/orether and/or imino group. The molecular weight of the compounds I ispreferably in the range from 50 to 2 000 daltons.

Particularly preferred compounds I have at least two and in particularexactly two primary amino groups and optionally further polar groupsselected from secondary amino groups, imino groups, OH functions andether groups.

Examples of preferred amines and aminoalcohols are: alkylene-diaminessuch as ethylene-1,2-diamine, propylene-1,2-diamine,propylene-1,3-diamine, butylenediamines, the monoalkyl, dialkyl andtrialkyl derivatives of these amines, for exampleN,N-dimethylpropylene-1,3-diamine, and also alkanolamines such asethanolamine and 3-aminopropanol. Monoalkylamines and alkylenediamineswhere the alkyl or alkylene radicals are interrupted by one or morenonadjacent oxygen atoms and may optionally also have hydroxyl groups orfurther amino groups such as 4,7-dioxadecane-1,10-diamine,2-(2-aminoethoxy)ethanol and N-(2-aminoethyl)ethanolamine are likewisesuitable. Further examples include N-amino-C₁-C₆-alkylpiperazines suchas 4-(2-aminoethyl)piperazine. Ethoxylated and/or propoxylatedderivatives of these amines and aminoalcohols are also suitable.

Useful alcohols are in particular di- or polyols preferably having from2 to 5 hydroxyl groups, for example glycol, glycerol, diglycerol,triglycerol, trimethylolpropane, pentaerythritol and also ethoxylatedand/or propoxylated derivatives of these di- and polyols. Particularlypreferred compounds I are the amines of the general formula IaH₂N—(R—NH)_(m)-A-(NH—R′)_(n)—NH₂   (Ia)where

-   -   A is C₂-C₂₀-alkylene which may be interrupted by one or more        nonadjacent oxygen atoms or is C₅-C₂₀-cycloalkylene;    -   R, R′ are each independently C₂-C₄-alkylene and    -   n, m are each independently from 0 to 5.    -   C₂-C₂₀-Alkylene is a divalent linear or branched alkyl group        having from 2 to 20 carbon atoms and the two free valences are        preferably on different carbon atoms. C₂-C₄-Alkylene is        accordingly, for example, 1,2-ethylene, or 1,2- or        1,3-propylene. C₂-C₂₀-Alkylene is therefore any of the groups        mentioned for C₂-C₃-alkylene or, for example, butane-1,2-diyl,        -2,3-diyl, -1,3-diyl or -1,4-diyl, pentane-1,2-diyl, -2,3-diyl,        -1,3-diyl, -1,4-diyl, -2,4-diyl or -1,5-diyl, hexane-1,6-diyl,        2,2,4-trimethylpentane-1,4-diyl, octane-1,8-diyl, etc. In the        alkylene groups, one or two carbon atoms may also be replaced by        oxygen atoms which are adjacent neither to each other nor to the        linkage sites. Such alkylene groups generally have from 5 to 20        carbon atoms. Examples thereof are: 3-oxapentane-1,5-diyl,        3-oxahexane-1,6-diyl, 4-oxaheptane-1,7-diyl,        3,6-dioxaoctane-1,8-diyl, 3,7-dioxanonane-1,9-diyl,        4,7-dioxadecane-1,10-diyl, 4,8-dioxaundecane-1,11-diyl,        4,9-dioxadodecane-1,12-diyl and 4,11-dioxatetradecane-1,14-diyl.

C₅-C₂₀-Cycloalkylene is a divalent mono- or bicycloaliphatic radicalpreferably having from 5 to 20 carbon atoms. Examples thereof arecyclopentane-1,2- and -1,3-diyl, cyclohexane-1,2-diyl, -1,3-diyl and1,4-diyl, cycloheptane-1,2-diyl, -1,3-diyl and 1,4-diyl,norbornane-2,3-diyl and 2,2-bis(cyclo-hexyl-4′-yl)propane.

Among the amines Ia, preference is given to those compounds where A isC₂-C₄-alkylene. R and R′ are preferably 1,2-ethylene or 1,3-propylene.The sum m+n preferably has a value from 1 to 10 and in particular from 2to 6. Examples of such amines are diethylenetriamine,triethylenetetramine, tetraethylenepentamine,N,N′-bis(3-aminopropyl)ethylenediamine,1,5-bis(3-aminopropyl-amino)-3-iminopentane and1,8-bis(3-aminopropylamino)3,6-bis-iminooctane.

The polyisobutene having a reactive end group content of at least 80%and a molecular weight distribution which is characterized by a maximumM_(p) in the range from 500 to 20 000 daltons and a ratio M_(W)/M_(N) of<1.4 is prepared according to the invention by a living cationicpolymerization process, as described, for example, in the previousGerman patent applications P 10061727.1 and P 10061751.8 which are fullyincorporated herein by way of reference.

In the process according to the invention, the polymerization ofisobutene is initiated by the initiator system comprising a Lewis acidand at least one compound II. It is assumed that the Lewis acid forms acarbocation or at least an ionic complex with the compound II orpolarizes the bond between the functional group FG and the carbon atomto which it is bonded so that there is an interaction with theolefinically unsaturated double bond of isobutene which generates apositive (partial) charge on the tertiary carbon atom of isobutene. Thisin turn interacts with a further isobutene molecule to continue thepolymerization reaction.

The terms “carbocation” and “cationic complex” are not strictly dividedfrom each other, but instead include all intermediate stages ofsolvent-separated ions, solvent-separated ion pairs, contact ion pairsand strongly polarized complexes having positive partial charge on onecarbon atom of compound II.

Compound II is also referred to hereinbelow as the initiator and theLewis acid as the coinitiator.

Examples of useful Lewis acids include the (semi)metal chlorides BCl₃,TiCl₄, VCl₅, SnCl₄ and FeCl₃. Preferred (semi)metal chlorides are BCl₃and in particular TiCl₄.

Preference is given to those compounds II where the functional group FGhas the general formula

where

-   -   X is selected from halogen, C₁-C₆-alkoxy and C₁-C₆-acyloxy,    -   R¹ is hydrogen or methyl and    -   R² is methyl, or forms a C₅-C₆-cycloalkyl ring with R¹ or with        the part of the molecule to which the functional group FG is        bonded, and R² may also be hydrogen when the functional group FG        is bonded to an aromatic or olefinically unsaturated carbon        atom.

The compounds of the general formula II preferably have one, two, threeor four, in particular one or two, and more preferably one, functionalgroup FG. X in the formula (FG) is preferably a halogen atom, inparticular chlorine.

Preferred compounds II correspond, for example, to the general formulaeII-A to II-D:

where X is as defined above,

-   -   k is from 0 to 10,    -   R³, R⁴ and R¹⁰ are each independently hydrogen or methyl,    -   R⁵, R⁶ and R⁷ are each independently hydrogen, C₁-C₄-alkyl or a        CR³R⁴—X group where R³, R⁴ and X are each as defined above and    -   R⁸ is hydrogen, methyl or an X group and    -   R⁹ and R⁹′ are each hydrogen or an X group.

In the formulae II-A to II-D, R³ and R⁴ are preferably both methyl. Informula II-A, R⁶ is, for example, a CR³R⁴-X group which is in thepara-position to the CR³R⁴X group when R⁵ is hydrogen. It may also be inthe meta-position when the R⁵ group is C₁-C₄-alkyl or a CR³R⁴-X group.Examples of preferred compounds II-A are 2-chloro-2-phenylpropane andalso 1,3- and 1,4-bis(2-chloro-2-propyl)benzene.

In formula II-B, R⁷ is preferably a CR³R⁴—X group or hydrogen. Examplesof compounds of the formula II-B are allyl chloride, methallyl chloride,2-chloro-2-methyl-2-butene and also 2,5-dichloro-2,5-dimethyl-3-hexene.

In the compounds II-C, R³ is preferably methyl. R² is preferablylikewise methyl. R⁹ is preferably an X group and in particular halogen,in particular when R¹⁰ is methyl. Examples of compounds of the generalformula II-C are 1,8-dichloro-4-p-menthane (limonene dihydrochloride),1,8-dibromo-4-p-menthane (limonene dihydrobromide),1-(1-chloroethyl)-3-chlorocyclohexane,1-(1-chloroethyl)-4-chlorocyclohexane,1-(1-bromoethyl)-3-bromocyclohexane and1-(1-bromoethyl)-4-bromocyclohexane.

Among the compounds of the formula II-D, preference is given to thosewhere R⁸ is a methyl group. Among the compounds of the formula II-D,preference is given to those compounds where k is 1, 2, 3 or 4. FG ispreferably halogen and in particular chlorine. With regard to the use ofthe polyisobutene derivatives as dispersants, preference is given to thecompounds II-D.

In general, the polyisobutenes which are intended for further processingto the PIB derivatives according to the invention will be prepared usingthe compound II in a quantity of at least 10⁻³ mol per mole ofisobutene, preferably in the range from 5×10⁻³ to 0.2 mol per mole, andin particular in the range from 0.01 to 0.1 mol per mole, of isobutene.It needs to be taken into account that the molecular weight achieved ofthe polyisobutene prepared by the process according to the inventiondepends on the amount of compound II such that the molecular weight ofthe polyisobutene decreases with the increasing amount of compound II,based on isobutene.

It will be appreciated that the Lewis acid is used for preparing thepolyisobutenes in the process according to the invention in an amountwhich is sufficient to form the initiator complex. In general, this isalready achieved at low concentrations of the Lewis acid in the reactionmedium, generally at least 0.01 mol/l. In general, the Lewis acid in thereaction medium will accordingly not exceed a concentration of 3 mol/l,preferably 2 mol/l and more preferably 1 mol/l. In particular, theconcentration is in the range from 0.1 to 2 mol/l and more preferably inthe range from 0.2 to 1 mol/l.

The molar ratio of Lewis acid to compound II will preferably not exceeda value of 1:1 and is in particular in the range from 1:1.2 to 1:10.

In addition to the compounds II, the initiator system preferablycomprises at least one further aprotic polar compound III which issuitable for complexing with the Lewis acid or with the carbocation orionic complex of the Lewis acid and compound II formed under thereaction condtiions. The compound III is a Lewis base (electron donor)which has at least one free electron pair on at least one heteroatomwhich is selected from, for example, oxygen, nitrogen, phosphorus andsulfur atoms.

Examples of such donor compounds III are pyridines such as pyridine andsubstituted pyridines, in particular sterically hindered pyridines, andalso N,N-dialkylamides of aliphatic or aromatic carboxylic acids such asN,N-dimethylacetamide, N-alkyl lactams such as N-methylpyrrolidone,dialkyl ethers such as diethyl ether and diisopropyl ether, cyclicethers such as tetrahydrofuran, trialkylamines such as triethylamine,C₁-C₄-alkyl esters of aliphatic C₁-C₆-carboxylic acids such as ethylacetate, dialkyl thioethers or alkyl aryl thioethers such as methylphenyl sulfide, dialkyl sulfoxides such as dimethyl sulfoxide,alkylnitriles such as acetonitrile and propionitrile,trialkyl-phosphines or triarylphosphines such as trimethylphosphine,triethylphosphine, tri-n-butylphosphine and triphenylphosphine, andnonpolymerizable, aprotic organosilicon compounds which have at leastone organic radical bonded via oxygen. This radical generally has from 1to 20 carbon atoms. Examples of such radicals are alkyloxy,cycloalkyloxy, aryloxy, arylalkyloxy and acyloxy (=alkylcarbonyloxy).

Among the abovementioned donors, preference is given to pyridine andsterically hindered pyridine derivatives and also in particularorganosilicon compounds. In a particularly preferred embodiment, thedonor used is at least one organosilicon compound.

Sterically hindered pyridines are those which have sterically demandingalkyl groups at least in the 2- and 6-positions of the pyridine ring,for example 2,6-diisopropyl-pyridine and 2,6-di-tert-butylpyridine.

Preference is given to using the donor III and in particular theorganosilicon compound in such an amount that the molar ratio of donormolecules III to the metal atoms or the semimetal atoms in the Lewisacid is in the range from 1:1 000 to 1:1, preferably in the range from1:500 to 1:1.5 and more preferably in the range from 1:200 to 1:2.

The organosilicon compounds suitable as donor III may have one or more,for example 2 or 3, silicon atoms with at least one organic radicalbonded via oxygen. Preference is given to those organosilicon compoundswhich have one, two or three, and in particular 2 or 3, organic radicalsbonded via oxygen per silicon atom.

Preferred organosilicon compounds are those which have the generalformula IIIa:R^(a) _(n)Si(OR^(b))_(4−n)   (IIIa)where n is 1, 2 or 3,

-   -   each R^(a) may be identical or different and may each        independently be C₁-C₂₀-alkyl, C₅-C₇-cycloalkyl, aryl or        aryl-C₁-C₄-alkyl, and the latter three radicals may also have        one more more C₁-C₁₀-alkyl groups as substituents, and    -   each R^(b) is identical or different and is C₁-C₂₀-alkyl or,        when n=1 or 2, two different R^(b) radicals may also form a 2-        or 3-membered alkylene unit.

In formula IIIa, the variable n is preferably 1 or 2. The variable R^(a)is preferably a C₁-C₈-alkyl group and in particular an alkyl group whichis branched or bonded via a secondary carbon atom, such as isopropyl,isobutyl, 2-butyl or a 5-, 6- or 7-membered cycloalkyl group. Thevariable R² is preferably a C₁-C₄-alkyl group.

Examples of such preferred compounds are dimethoxydiisopropyl-silane,dimethoxyisobutylisopropylsilane, dimethoxydiisobutyl-silane,dimethoxydicyclopentylsilane, dimethoxyisobutyl-2-butyl-silane,diethoxyisobutylisopropylsilane, triethoxytoluylsilane andtriethoxybenzylsilane.

Useful isobutene feedstocks for the process according to the inventionare both isobutene itself and also isobutenic C₄-hydrocarbon streams,for example C₄-raffinates, C₄-cuts from isobutane dehydrogenation, andC₄-cuts from steam crackers and FCC crackers (FCC: Fluid CatalyzedCracking), as long as they have been substantially freed of1,3-butadiene contained therein. C₄-Hydrocarbon streams suitableaccording to the invention generally comprise less than 5 000 ppm,preferably less than 2 000 ppm, of butadiene. When C₄-cuts are used asstarting materials, the hydrocarbons other than isobutene assume therole of an inert solvent.

Useful solvents include all low molecular weight organic compounds whichare different to compounds II and III and also to isobutene, have noabstractable protons and are liquid under the polymerization conditions,optionally as a mixture of solvents. Preferred solvents arehydrocarbons, for example acyclic alkanes having from 2 to 8, andpreferably from 3 to 6, carbon atoms such as ethane, iso- and n-propane,n-butane and its isomers, n-pentane and its isomers, n-hexane and itsisomers and also n-heptane and its isomers, cyclic alkanes having from 5to 8 carbon atoms such as cyclopentane, cyclohexane and cycloheptane,acyclic alkenes preferably having from 2 to 8 carbon atoms such asethene, iso- and n-propene, n-butene, n-pentene, n-hexene and n-heptene,cyclic olefins such as cyclopentene, cyclohexene and cycloheptene,aromatic hydrocarbons such as toluene, xylene and ethylbenzene, and alsohalogenated hydrocarbons, for example halogenated alkanes having from 1to 5 carbon atoms and 1, 2, 3, 4, 5 or 6 halogen atoms selected fromfluorine and in particular chlorine, such as methyl chloride,dichloromethane, trichloromethane, ethyl chloride, 1,2-dichloroethaneand 1,1,1-trichloroethane and also chloroform and haloaromatics such aschlorobenzene.

Not only the solvents alone, but also mixtures of these solvents aresuitable. Preference is given to mixtures in particular when the solventhas a melting point above the desired polymerization temperature.

Particular preference is given to solvents and solvent mixtures whichcomprise at least one hydrocarbon. Among these, particular preference isgiven to solvent mixtures which comprise at least one hydrocarbon and atleast one haloalkane. Among these, particular preference is given tosolvent mixtures which comprise at least one acyclic alkane having from4 to 6 carbon atoms, in partiuclar hexane, and at least onechloroalkane, in particular methyl chloride or methylene chloride.Particular preference is likewise given to solvent mixtures whichcomprise at least one aromatic hydrocarbon, in particular toluene, andat least one chloroalkane, in particular methyl chloride or methylenechloride. The volume ratio of hydrocarbon to halogenated hydrocarbon ispreferably in the range from 1:10 to 10:1, in particular in the rangefrom 4:1 to 1:4. It will be appreciated that the chloroalkanes in thesemixtures comprise no compounds in which chlorine atoms are attached tosecondary or tertiary carbon atoms. Particular preference is likewisegiven to ternary solvent mixtures which comprise at least one aromatichydrocarbon, in particular toluene, at least one acyclic alkane havingfrom 4 to 6 carbon atoms, in particular hexane, and at least onechloroalkane, in particular methyl chloride or methylene chloride. Thevolume ratio of the three components mentioned is selected in such amanner that the ratio of alkane to aromatic is in the range from 1:10 to10:1 and the volume ratio of alkane+aromatic to haloalkane is in therange from 10:1 to 1:1. When the polymerization is carried out withevaporative cooling, the solvent or solvent mixtures then also containup to 50% by volume, for example from 5 to 50% by volume, preferablyfrom 10 to 30% by volume, of a volatile solvent component, for exampleethylene.

It will be appreciated that the polymerization is carried out undersubstantially aprotic, in particular anhydrous, reaction conditions.Aprotic and anhydrous reaction conditions mean that the water contentand protic impurity content respectively in the reaction mixture areless than 50 ppm and in particular less than 5 ppm. In general, thestarting materials will accordingly be dried by physical and/or chemicalmeasures before use. For example, the aliphatic or cycloaliphatichydrocarbons preferably used as solvent after customary prepurificationand predrying may be admixed with an organometallic compound, forexample an organolithium, organomagnesium or organoaluminum compound ina sufficient amount to remove water traces from the solvent. The solventtreated in this manner is then condensed directly into the reactionvessel. It is also possible to proceed in a similar manner with thea-olefins, the aromatic hydrocarbons and the monomers to be polymerized,in particular the isobutene.

The solvents and the isobutene are prepurified and predried in acustomary manner, preferably by treating with solid drying agents suchas molecular sieves or predried oxides such as calcium oxide or bariumoxide. A similar method may be used to dry the starting materials forwhich treatment with metal alkyls is unsuitable, for example the alkylhalides used as solvent and also compounds II and III.

In general, the process according to the invention will be carried outat temperatures below room temperature (25° C.) and preferably below 0°C., for example in the range from 0 to −140° C., preferably in the rangefrom −30 to −120° C., and more preferably in the range from −40 to −110°C. In general, the greater the purity of the reactants used, the higherthe possible reaction temperatures. The reaction pressure is of minorimportance and depends in a known manner on the apparatus used and otherreaction conditions.

The isobutene or isobutenic starting material polymerizes spontaneouslywhen the initiator system used according to the invention is mixed withthe isobutene or isobutenic starting material in the inert organicsolvent at the desired reaction temperature. A possible procedure is toinitially charge isobutene in the inert solvent, cool it to reactiontemperature and then add the initiator system. Another possibleprocedure is to initially charge the initiator system in the solvent andthen add the isobutene or isobutenic feedstock, either all at once or atits rate of consumption. Also, a portion or the entire amount of theisobutene or isobutenic feedstock may be initially charged in thesolvent and then the initiator system added. The remaining amounts ofisobutene or isobutenic feedstock are then introduced in the course ofthe reaction, for example at the rate of their consumption. When theinitiator system is added, the procedure will generally be to add thecomponents of the initiator system separately. In the batchwise methoddescribed here, the procedure will generally be to first add theinitiator compound II and any compound III and then the Lewis acid(coinitiator). The initiation time is the time at which both componentsof the initiator system are contained in the reaction vessel. An exampleof a possible procedure is to initially charge the solvent, thencompound II and any donor III and then a portion or the entire amount ofthe isobutene or isobutenic feedstock, and then to introduce anyremaining amount of isobutene or isobutenic feedstock to thepolymerization. However, it is also possible to initially charge firstthe solvent, then the Lewis acid and a portion or the entire amount ofisobutene or isobutenic feedstock and then start the polymerization byadding compound II and any compound III. Preference is given to addingthe coinitiator into a reaction vessel which already contains isobuteneand any comonomers, and then further amounts of isobutene and any Lewisacid may also be added under polymerization conditions in the course ofthe polymerization reaction (in general, also referred to as incrementalmonomer addition).

As well as the above-described batchwise procedure, the polymerizationmay also be configured as a continuous process. The feedstocks, i.e. themonomers to be polymerized, the solvent and also the initiator system ofthe polymerization reaction, are added continuously and the reactionproduct is withdrawn continuously, so that more or less stationarypolymerization conditions are maintained in the reactor. The componentsof the initiator system may be introduced either separately or elsetogether, preferably diluted in the solvent. The isobutene or isobutenicfeedstocks to be polymerized may be added alone, diluted with a solventor as an isobutenic hydrocarbon stream. For example, the components ofthe initiator system diluted in the solvent may be added viamulticomponent jets in order to achieve good mixing of the components.

The heat of reaction in both the batchwise and continuous reactionprocedure is removed in a customary manner, for example using internallyinstalled heat exchangers and/or by wall cooling and/or by utilizingevaporative cooling. The use in particular of ethene and/or mixtures ofethene with other hydrocarbons and/or halogenated hydrocarbons assolvent has proven useful, since ethene is not only inexpensive, butalso has a boiling point in the desired polymerization temperaturerange.

Useful reaction vessels for carrying out the process according to theinvention include in principle all reactors that are customarily used incationic polymerization of isobutene, for example cationicpolymerization of isobutene using boron trifluoride-oxygen complexes. Inthis regard, reference is hereby made to the relevant prior art. Whenthe reaction is carried out batchwise, useful reactors include thecustomary stirred tanks which are preferably equiped with evaporativecooling, suitable mixers, feeds, heat exchanger elements andinertization devices. The continuous reaction may be carried out incustomary reaction tanks, reaction batteries, tubular reactors, tubebundle reactors, and in particular circular or helical tubular and tubebundle reactors which have preferably been equipped in the mannerdescribed above for reaction tanks.

Useful reactors for the continuous preparation of polyisobutenes are inparticular tubular reactors. Among these, preference is given to thosein which very little backmixing takes place, since particularly narrowmolecular weight distributions are obtained. The use of a spiral flowreactor, also referred to as a spiral tubular reactor, with appropriatehelical winding avoiding differing flow rates in the center region andin the wall region of the tube (flow profile), is ideal. Theinstallation of static mixers or similar internals allows good mixingand in particular good heat removal to be achieved, even when the flowis laminar.

To recover the polyisobutenes from the reaction mixture, it isdeactivated after the polymerization in the manner customary forcationic polymerization reactions, preferably by adding a proticcompound, in particular by adding alcohols such as methanol, ethanol,n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol ortert-butanol, or mixtures thereof with water. Preference is given toadding the substances used for deactivation in a diluent, for exampleone of the abovementioned solvents, in order to avoid an undesiredviscosity increase. Reference is also hereby made to the prior art forpolymerizing boron trifluoride with isobutene cited at the outset whoseworkup measures may be applied in a similar manner to the processaccording to the invention.

Preference is given to cooling the means used for deactivation or themixture thereof with an inert solvent to the polymerization temperaturebefore the deactivation, in order to avoid undesired secondaryreactions. Thereafter, the mixture will generally be heated totemperatures above 0° C. and the reaction mixture washed with water ormethanol or a mixture thereof. After removal of aqueous components, themixture is optionally dried.

In general, the solvents are then removed in suitable units, for examplein rotation, falling film or thin film evaporators, or by flashevaporation (depressurization of the reaction solution downstream of atube bundle heat exchanger in tube lines or using a perforated jetplate). In general, reduced pressure, for example in the range from 0.1to 800 mbar, preferably from 1 to 100 mbar, will be applied to removethe solvent. The bottom temperature is preferably from 50 to 250° C. andin particular from 150 to 230° C. The use of elevated temperatures, forexample above 150° C., in particular 170° C. or higher, leads to afurther reduction in the residual chlorine contents and accordingly toan increased proportion of terminal double bonds in the reactionproduct.

The polyisobutenes prepared in this manner have a high content ofolefinically unsaturated end groups of the general formula (A) and/or(B). The end group content is generally at least 80 mol %, in particularat least 90 mol % and more preferably at least 95 mol %, based on thepolymer chains. The polyisobutenes prepared in this manner have a narrowmolecular weight distribution which is characterized by a polydispersityD=M_(W)/M_(N) of below 1.4, preferably below 1.3, and in particularbelow 1.2, for example in the range from 1.05 to 1.2.

Advantageously, the polyisobutenes obtained in this manner are notable,as well as for the low polydispersity, in that the maximum of themolecular weight distribution M_(p) is less than 10% above the value ofthe number average molecular weight. In many cases, the peak maximumM_(p) is even less than 8% or even less than 6% above the value of thenumber average molecular weight.

All molecular weights quoted refer to values as determined by means ofgel permeation chromatography (GPC). The gel permeation chromatographywas effected using THF as the eluent and CS₂ as the reference in twocolumns attached in series (L=300 mm, d=7.8 mm), the first of which waspacked with Styragel HR5 (molecular weight ratio 50 000 to 4×10⁶) andthe second of which was packed with styragel HR3 (molecular weight range200 to 30 000) from Waters. The detection was effected using adifferential refractometer. The standards used for determining theisobutene block were commercial polyisobutene standards in the molarmass range from 224 to 1 000 000 from Polymer-Standards Service, Mainz.The elution diagrams were evaluated with regard to the polydispersityM_(W)/M_(N) in such a manner that the reference value of 1.7 wasobtained for commercial polyisobutene of molar mass 1 000 (Glissopal®1000 from BASF-Aktiengesellschaft).

The polyisobutenes obtained in this manner may then be reactedsuccessively in a known manner with maleic anhydride and then with thealcohol, amine or aminoalcohol or a mixture thereof. Processes for thispurpose are disclosed by, for example, DE-A 27 02 604, U.S. Pat. No.4,152,499, U.S. Pat. No. 5,137,980 and also DE-A 43 19 672 which areexplicitly incorporated herein by way of reference.

To this end, the polyisobutene is reacted thermally in a first step in amanner known per se with maleic anhydride. Maleic anhydride andpolyisobutene are generally reacted with each other in a molar ratio inthe range from 0.7:1 to 4.0:1, preferably from 0.8:1 to 2.5:1 and inparticular from 0.9:1 to 1:1.5. Excess unconverted maleic anhydride mayoptionally be removed from the reaction mixture after the end of thereaction extractively or distillatively, for example by stripping withinert gas at elevated temperaute and/or reduced pressure.

The reaction is generally carried out at a temperature in the range from100 to 300° C., preferably from 120 to 270° C. and in particular from150 to 250° C. The reaction time is generally from 50 minutes to 20hours and preferably in the range from 1 to 6 hours.

Preference is given to carrying out the reaction with exclusion ofoxygen and water in order to avoid undesired secondary reactions.However, the degree of conversion in the presence of air or a few ppm ofhalogen such as bromine may be higher than under inert conditions. Thereaction will accordingly preferably be carried out using appropriatelypurified reactants and in an inert gas atmosphere, for example underdried nitrogen, since the low extent of by-product formation allows theomission of a subsequent filtration step.

If desired, the reaction may be carried out in a solvent which is inertunder the reaction conditions, for example in order to achieve asuitable viscosity of the reaction mixture or in order to avoidcrystallization of maleic anhydride on cold spots of the reactor.Examples of useful solvents are aliphatic hydrocarbons and mixturesthereof, for example those mentioned above, in particular paraffins andoils having a boiling point above the reaction temperature and alsoaromatic hydrocarbons and halogenated hydrocarbons such as toluene,xylene, isopropylbenzene, chlorobenzene and dichlorobenzene, and alsomixtures of the abovementioned solvents.

The polyisobutene functionalized in the first step with maleic anhydridePIB-MA is then reacted with the compound I, generally in a molar ratioof PIB-MA to compound I in the range from 0.4:1 to 4:1 and preferablyfrom 0.5:1 to 3:1. In compounds having only one primary or secondaryamino group, at least equimolar quantities of amine will frequently beused.

When the preferred primary amines are used, the reaction with the maleicanhydride group of the functionalized polyisobutene may also form amideand/or imide structures, and the reaction conditions are preferablyselected in such a manner that imide structures are formed, since theproducts obtained are preferred owing to their better applicationproperties.

Particularly preferred amines having at least two, preferably primary,amino groups are able to form bisamides or bisimides which areparticularly preferred according to the invention. To prepare thebisimides, the amine will preferably be used in approximately thedesired stoichiometry. Preference is given to using these diamines in anamount of less than 1 mol, in particular in an amount of from 0.3 to0.95 mol and more preferably in an amount of from 0.4 to 0.9 mol permole of PIB-MA.

The reaction of the polyisobutene functionalized using maleic anhydridewith compound I is, depending on the reactivity of the compound I used,generally carried out at a temperature in the range from 25 to 300° C.,preferably from 50 to 200° C. and in particular from 70 to 170° C.,optionally using an amidation catalyst. Excess unconverted compound Imay optionally be removed from the reaction mixture after the end of thereaction extractively or distillatively, for example by stripping usinginert gas at elevated temperature and/or under reduced pressure.Preference is given to carrying out the reaction to a conversion of thecomponents of at least 90% and in particular 95% (based on thecomponents used in deficiency), and the reaction progress may befollowed using the water content by means of customary analyticalmethods, for example via the acid number. The formation of compoundshaving imide structure from those having amide structure can be followedby means of IR spectrometry.

The derivatives of polyisobutene according to the invention are notablefor their improved viscosity behavior at a dispersancy at leastcomparable to commercial products having comparable number averagemolecular weight. They may accordingly be used in higher concentrationsthan commercial dispersants without any danger of disadvantageousviscosity behavior of the lubricant, which is of interest in particularwith regard to lengthened oil change intervals.

Surprisingly, even mixtures of the polyisobutenyl derivatives accordingto the invention which comprise a component having a relatively lowmolecular weight and a further component having a relatively highmolecular weight lead to better application properties than a derivativeobtained from a commercial polyisobutene whose weight average molecularweight M_(W) corresponds to the average of the number average molecularweights of this mixture. Accordingly, mixtures of polyisobutenylderivatives according to the invention likewise form part of thesubject-matter of the present invention. The mass ratio of the lowmolecular weight to the high molecular weight components may be in therange from 1:10 to 10:1. The mixing may take place at the polyisobutenestage. However, preference is given to mixing the low molecular weightand the high molecular weight polyisobutenyl derivative, since evenbetter application properties are then obtained.

For this reason, a further aspect of the present invention relates tothe use of the polyisobutene derivatives according to the invention asadditives in liquid lubricant compositions, in particular in lubricantoils for combustion engines such as Otto, Wankel, two-stroke and dieselengines and especially in fuel economy engine oils. Fuel economy engineoils are oils for combustion engines whose dynamic viscosity at −35° C.is below 60 000 mPa.s (ASTM/D 4684) and whose dynamic viscosity at −25°C. is below 3 500 mPa.s (by DIN 51377).

The polyisobutene derivatives according to the invention are generallyadded to the lubricants in the form of a from 50 to 60% mineral oilsolution, customarily in an amount of from 0.5 to 25% by weight,preferably in an amount of from 1 to 20% by weight and in particular ina from 2 to 15% by weight solution (based on a 50% by weight solution),based on the total weight of the composition. Lubricant compositionswhich comprise these amounts of polyisobutene derivatives according tothe invention accordingly likewise form part of the subject-matter ofthe present invention.

In principle, useful lubricants include all liquid lubricants (seeabove), preferably oils for combustion engines in motor vehicles, i.e.oils for Otto, Wankel, two-stroke and diesel engines, in particular fueleconomy engine oils and especially those of viscosity classes 5 W to 20W by DIN 51511.

The liquid lubricants may be additivized in the customary manner, i.e.as well as the base oil components typical for the application, theycomprise, for example, mineral or synthetic hydrocarbons, polyethers oresters and mixtures thereof, further additives other than dispersantssuch as detergent additives, antioxidants, viscosity index improvers,pour point depressants, friction modifiers, defoamers, corrosioninhibitors, etc., in the customary amounts. An overview of suitableadditives can be found in D. Klamann, “Lubricants and RelatedProducts—Additives” in Ullmanns Encyclopedia of Industrial Chemistry,5th ed. on CD-ROM, WILEY-VCH 1999.

It will be appreciated that the additives according to the invention mayalso be used together with other dispersing additives, and theproportion of polyisobutene derivatives according to the invention inthe total quantity of dispersing additives is generally at least 30% byweight and preferably at least 60% by weight.

Surprisingly, it has been found in connection with the dispersantsaccording to the invention that polyisobutenes having a molecular weightdistribution which is characterized by a maximum M_(p) in the range from20 000 to 120 000 and a polydispersity M_(W)/M_(N) of <1.4 provide anoutstanding improvement in the viscosity behavior of liquid lubricantcompositions, in * particular of synthetic and/or mineral hydrocarbons,as used in combustion engines, in particular motor vehicle engines.

In particular, they lead to improve thickening at high temperatures,improved viscosity behavior at low temperatures and better shearstability of the lubricant in comparison to known viscosity indeximprovers (VI-improvers) based on polyisobutenes or olefin copolymers(OCP=ethene/propene copolymers).

The polyisobutenes suitable for use as VI-improvers may likewise beprepared in the above-described manner, although to obtain a relativelyhigh molecular weight, compound II is used in relatively small amounts,preferably in an amount of from 10⁻⁴ to 10⁻² mol per mole of isobuteneand in particular in an amount of from 5×10⁻⁴ to 5×10⁻³ mol per mole ofisobutene. The ratio of Lewis acid to compound II will, owing to therelatively low concentration of compound II, exceed the value 1:1 andmay be up to 1:20. It is preferably in the range from 1:30 to 1:20. Theratio of donor III to Lewis acid is preferably in the range from 1:100to 1:1, in particular in the range from 1:50 to 1:1.1 and morepreferably in the range from 1:20 to 1:1.5. Otherwise, the same appliesas was stated for preparing PIB having a molecular weight in the rangefrom 500 to 20 000.

The PIBs obtained in this manner are characterized by a molecular weightdistribution having a maximum MP in the range from >20 000 to 120 000and a polydispersity M_(W)/M_(N) of below 1.4 and may be used with orwithout a customary functionalization or hydrogenation of the terminaldouble bond as VI-improvers in liquid lubricants, in particular in thelubricants mentioned as being preferred. The PIBs lead to a viscositybehavior comparable with conventional polyisobutenyl derivatives ofsuccinic acid at relatively low temperature, but have better shearstability. The thickening action is comparable to or frequently betterthan the known VI-improvers based on polyisobutenes having the sameweight average molecular weight M_(W) , so that relatively smallquantities are required to achieve the specification. The concentrationof such PIBs in lubricants, in particular in fuel economy engine oils,is in the customary ranges, for example in the range from 0.1 to 20% byweight, in particular from 0.2 to 10% by weight and more preferably from0.5 to 5% by weight, based on the total weight of the composition.

The invention is illustrated by the examples hereinbelow.

I. Analysis

The molecular weight (M_(N), M_(W)) was determined in theabove-described manner by means of GPC, mass spectrometry and/or by ¹HNMR spectroscopy. The double bond content was determined by means of ¹HNMR spectroscopy (integration of the vinyl protons compared to methyland methylene protons) or via the chlorine content. The residualchlorine content was determined by elemental analysis.

II. Preparation of the polyisobutene Derivatives

IIa. Preparation of the polyisobutenes (Preparative Examples 1 to 3)

1. Preparation of a polyisobutene having an M_(n) of 2 300

The reaction vessel used was a 2 l four-neck flask which was equippedwith a dry ice condenser, a 1 l dropping funnel having a molecular sievebed (3 Å; 500 ml; dried at 150° C./2 mbar for 16 h) and a dry icecondenser, a thermometer, a septum, a magnetic stirrer and a further 1 ldropping funnel which had a molecular sieve bed (3 Å; 300 ml; dried at150° C. and 2 mbar for 16 h) and above it a bed of 250 ml of an acidicion exchanger (Lewatit K 2621 from Bayer AG; dried at 150° C. and 2 mbarfor 16 hours) and also a dry ice condenser. The reaction vessel wasdried by evacuating it and purging it with dry nitrogen twice. A mixtureof 600 ml of dried methylene chloride and 200 ml of dried hexane cooledto −78° C. was charged into the dropping funnel having the molecularsieve and ion exchanger so that the molecular sieve and ion exchangerwere covered. After 15 min, the solvent mixture was added dropwise intothe reaction vessel within 30 min. 448.9 g (8 mol, 750 ml) of isobutenewere condensed into the other dropping funnel (having the molecularsieve) in such a manner that the isobutene was dried on a furtherpacking of 250 ml of molecular sieve 3 Å at an average residence time of15 min, based on the dead volume of the molecular sieve. This isobutenewas added dropwise into the reaction flask within a total of 25 minutesat an average residence time on the molecular sieve in the droppingfunnel of 15 minutes. 0.38 g (2 mmol) of 2,6-di-tert-butylpyridine and45.1 g (0.22 mol) of tetraisobutenyl chloride were added with stirringvia the septum and the reaction flask was cooled using dry ice to −70°C. 22.8 g (0.12 mol) of titanium tetrachloride were then added via theseptum with vigorous stirring. The polymerization which then begins canbe recognized by the temperature increase in the reaction vessel. After5 minutes, the reaction was ended by adding 77 ml (1 mol) ofisopropanol, the reaction mixture heated to 0° C. and washed three timeswith 200 ml of water each time, dried over sodium sulfate and freed ofsolvent at 200° C. under reduced pressure to a final pressure of 2 mbarand then treated with basic aluminum oxide.

Yield: 490 g of clear oil, M_(N)=2 300 D, M_(p)=2 350, D=1.18; viscosityat 100° C.: 1 250 mm²/s; chlorine content below 12 ppm, content ofolefinic end groups A: 65 mol %, end groups B: 30 mol %.

2. Preparation of a polyisobutene having an M_(n) of 3 900

The reaction was carried out in a similar manner to preparative example1, except that 200 ml of methylene chloride, 366.7 g (6 mol) ofisobutene, 16.4 g (80 mmol) of tetraisobutenyl chloride and 7.6 g (40mmol) of titanium tetrachloride were used.

Yield: 340 g of clear oil, M_(N)=3 900, M_(p)=4 100, M_(W)=4 300,D=1.19; viscosity at 100° C.: 3 200 mm²/s; chlorine content below 1 ppm,content of olefinic end groups A: 65 mol %, end groups B: 28 mol %.

3. Preparation of a polyisobutene having an M_(n) of 74 000

Preparative example 3 was carried out in a similar manner to preparativeexample 1, except that 600 ml of hexane, 200 ml of methyl chloride,224.4 g (4 mol) of isobutene, 1.23 g (6 mmol) of tetraisobutenylchloride and 11.4 g (60 mmol) of titanium tetrachloride were used;methyl chloride was condensed in together with isobutene and addeddropwise; the reaction time was 20 hours at −78° C.

Yield: 220 g of a clear oil, M_(N)=74 000, M_(p)=80 000, D=1.11; theviscosity of a solution of 2 g of polyisobutene in 10 ml of isooctane at20° C. was 1.30 mm²/s; chlorine content 9 ppm (there was noaftertreatment using Al₂O₃).

IIa. Preparation of the polyisobutene-succinic acid Derivatives

EXAMPLE 1

400 g of the polyisobutene obtained from preparative example 1 wereheated with 4 g of 2-propanol in a 1.2 l stirred autoclave equipped witha pan stirrer to 160° C. at a pressure of 10 mbar. With the vacuum linesclosed, 25.5 g of liquid maleic anhydride were then metered directlyonto the pan stirrer, and the mixture was heated at the same time.

When the metering in had ended, the internal temperature was 205° C.,and after a further 10 min, 225° C. The autoclave contents were stirredat 225° C. for a further 4 hours, and the pressure in the reactor firstdecreased to 1 bar of superatmospheric pressure, then increased to 2bar. The heating of the autoclave was then switched off and it wascautiously depressurized. Vacuum was then applied cautiously at 200° C.so that volatilizing maleic anhydride did not lead to foam overflow. Inthis manner, unconverted maleic anhydride was removed at 200° C. to afinal vacuum of 1 mbar.

The active substance content was then determined by means of columnchromatography and was 81%. The saponification number was 46 mg of KOH/gof substance. 400 g of the product obtained in this manner (0.164 mol)of polyisobutene succinic anhydride (PIBSA) were reacted with 15.53 g oftetraethylenepentamine (0.082 mol of TEPA) in a rotary evaporator at atemperature of 180° C. for 4 hours. A pressure of 1 mbar was then setfor 15 minutes. A low viscosity mineral oil (SN 100) was then added insuch a quantity that the concentration of the active product was 60% byweight.

EXAMPLE 2

The polyisobutene obtained from preparative example 2 was reacted in asimilar manner to example 1. After the first stage, the active substancecontent was about 75% by weight, and the saponification number was 22 mgof KOH/g of product.

COMPARATIVE EXAMPLE 1

Commercial polyisobutene having M_(W)=1 630, M_(N)=1 000 and apolydispersity of 1.63 was reacted in a similar manner to example 1.

COMPARATIVE EXAMPLE 2

Commercial polyisobutene having M_(W)=4 370, M_(N)=2 300 and apolydispersity of 1.90 was reacted in a similar manner to example 1.

III Application Testing

1. Dispersancy

To assess the dispersancy, a spot test according to “Les Huiles pourMoteurs et la Graissage des Moteurs” by A. Schilling, 1962, Vol. 1, page89 ff. was carried out. To this end, a diesel oil-carbon blackdispersion having a 3% by weight content of the additive to be testedwas prepared. A drop of the dispersion was applied to a filter paper forpaper chromatography and the carbon black migration was assessedvisually with reference to a scale from 0 to 1 000. The higher thevalue, the better the dispersancy. Table 1 shows the results.

2. Viscosity at a High Shear Rate

The viscosity at high shear rate was determined by DIN 51377.

To this end, the additives of examples 1 and 2 and comparative example 1were each mixed with a customary fuel economy oil formulation in anamount of 5% by weight, based on the formulation. The results arereported in table 1. Examples 1 and 2 achieved the specification OW-30,but the comparative examples C1 and C2 did not. TABLE 1 PIB derivativeViscosity at −30° C. Experiment Ex. Dispersancy [mPa · s] 1 1 665 3 0002 2 685 3 200 3 C2 635 3 400

3. Shear Stability

The shear stability of the oil was determined by measuring the viscosityloss in a Bosch nozzle by DIN 51382 (results in %, based on the startingviscosity). To this end, a fuel economy engine oil formulation 5W-40having the polyisobutene from preparative example 3 (PIB 3) wasadditivized for 10W40 in accordance with the specification.

For comparative purposes, a fuel economy oil formulation was additivizedfor 5W-40 engine oil in accordance with the specification using eitheran olefin copolymer OCP (characterization) and a commercialpolyisobutene (PIB C2) having a molecular weight M_(N) of 74 000 and apolydispersity of 3.0. The amounts required in each case and results arereported in table 2. TABLE 2 Experiment Polymer Amount [% by weight]Shear loss 4 PIB 3 1.5  4% 5 PIB C2 2.5 15% 6 OCP 1.5 10%

1-19. (canceled)
 20. A polyisobutenyl derivative of succinic acidobtainable by: i) reacting a polyisobutene which has a reactive endgroup content of at least 80% and whose molecular weight distribution ischaracterized by a maximum M_(P) in the distribution curve in the rangefrom 500 to 20 000 daltons and a ratio of weight average molecularweight to number average molecular weight M_(W)/M_(N) of below 1.4 withmaleic acid or maleic anhydride; ii) reacting the polyisobutene-succinicacid derivative obtained in i) with at least one compound I which has atleast one primary or secondary amine group and/or an OH group to form anamide or ester bond.
 21. A polyisobutenyl derivative as claimed in claim20 where the polyisobutene has a molecular weight distribution having amaximum M_(P) in the range from 1 500 to 15
 000. 22. A polyisobutenylderivative as claimed in claim 20 where the compound I has at least oneprimary amino group.
 23. A polyisobutenyl derivative as claimed in claim22 where the compound I is selected from diamines of the general formulaIaH₂N—(R—NH)_(m)-A-(NH—R′)_(n)—NH₂   (Ia) where A is C₂-C₂₀-alkylene whichmay be interrupted by one or more nonadjacent oxygen atoms or isC₅-C₂₀-cycloalkylene; R, R′ are each independently C₂-C₄-alkylene and n,m are each independently from 0 to
 5. 24. A process for preparingpolyisobutenamines of the general formula I as claimed in claim 20 whichcomprises polymerizing isobutene in the presence of an initiator systemcomprising a) a Lewis acid selected from covalent metal chlorides andsemimetal chlorides, b) and at least one compound II having at least onefunctional group FG which forms a carbocation or a cationic complexunder polymerization conditions and is selected from halogen, acyloxyand alkoxy which are bonded to a secondary or tertiary aliphatic carbonatom, to an allylic carbon atom or to a benzylic carbon atom, in asolvent which is inert toward the Lewis acid at a molar ratio of Lewisacid to compound II in the range from 10:1 to 1:100 to obtain apolyisobutene having an olefinic end group content of at least 80 mol %whose molecular weight distribution has a maximum M_(P) in the rangefrom 500 to 20 000 and a polydispersity M_(W)/M_(N) below 1.4, andreacting the polyisobutene obtained in this manner successively withmaleic acid or maleic anhydride and then with a compound I which has atleast one primary or secondary amine group and/or OH group.
 25. Aprocess as claimed in claim 24 where the compound II is selected fromcompounds of the general formulaCH₃—C(CH₃)₂—[CH₂—C(CH₃)₂]_(k)—X where k is 0, 1, 2, 3 or 4 and X ishalogen, alkyloxy or acyloxy.
 26. A process as claimed in claim 24,wherein the compound II is used in a quantity of from 0.001 to 0.3 molper mole of isobutene.
 27. A process as claimed in claim 24, wherein theLewis acid is selected from titanium (IV) chloride and borontrichloride.
 28. A process as claimed in any one of claims 24 to 27,wherein the initiator system additionally has at least one aprotic polarcompound III which is suitable for complex formation with the Lewis acidor with the carbocation or cationic complex formed under the reactionconditions from the Lewis acid and compound II.
 29. A process as claimedin claim 28, wherein compound III is selected from pyridine,alkylpyridines and nonpolymerizable, aprotic organosilicon compoundshaving at least one Si—O bond.
 30. A process as claimed in claim 27,wherein compound II and compound III are used in a III:II molar ratio inthe range from 1:1 to 1:1
 000. 31. A process as claimed in claim 24,wherein the solvent for the polymerization is selected from hydrocarbonshaving from 2 to 10 carbon atoms, inert halogenated hydrocarbons havingfrom 1 to 3 carbon atoms and mixtures thereof.
 32. A process as claimedin claim 24, wherein the polyisobutenes are recovered by removing thesolvent at temperatures of at least 150° C.
 33. A lubricant composition,comprising at least a polyisobutene derivative as defined in claim 20 asan additive.
 34. A lubricant composition comprising, in addition tocustomary additive components, at least one polyisobutene derivative asclaimed in claim 20 in quantities of from 0.5 to 25% by weight, based onthe total weight of the composition.
 35. A lubricant composition asclaimed in claim 34 in the form of a fuel economy engine oil.
 36. Alubricant composition comprising at least one polyisobutene having amaximum M_(P) in the molecular weight distribution in the range from >20000 to 120 000 and a polydispersity M_(W)/M_(N) of below 1.4 in aquantity of from 0.5 to 5% by weight, based on the total weight of thecomposition.
 37. A lubricant composition as claimed in claim 36additionally comprising at least one polyisobutene derivative ofsuccinic acid in a quantity of from 0.5 to 25% by weight, wherein saidat least one polyisobutene derivative of succinic acid is the reactionproduction of: i) reacting a polyisobutene which has a reactive endgroup content of at least 80% and whose molecular weight distribution ischaracterized by a maximum M_(P) in the distribution curve in the rangefrom 500 to 20 000 daltons and a ratio of weight average molecularweight to number average molecular weight M_(W)/M_(N) of below 1.4 withmaleic acid or maleic anhydride; ii) reacting the polyisobutene-succinicacid derivative obtained in i) with at least one compound I which has atleast one primary or secondary amine group and/or an OH group to form anamide or ester bond.